The present invention relates to the preparation of tea products and more particularly to water soluble tea extracts prepared by acid hydrolysis of the spent tea residues formed during the hot aqueous extraction of tea leaves in the production of water soluble tea extracts.
The products of tea have been increasingly marketed in the form of water-soluble tea extracts, usually in the form of dry powders. Substantial research activity has been directed to improve the quality of tea beverage, having a flavour and colour as close as possible to that obtained by brewing tea leaves. Another aspect of soluble tea manufacturing is to increase the yield of tea soluble solids.
Methods of obtaining tea extracts from tea leaves using a series of countercurrent stages or a two-stage extraction are well-known. Temperatures of aqueous extraction vary from room temperature to elevated temperatures as high as 180.degree. C. with elevated pressures.
However, the predominantly remaining spent tea, i.e., tea extraction residue material, is currently discarded.
In U.S. Pat. No. 4,668,525, a method is described for treating the spent tea leaf from a tea extraction process which comprises acidifying the spent tea leaf to reduce the pH to within the range of about 2.0 to 3.0 and subjecting the acidified spent tea leaf to further extraction with aqueous solvent at pressures of about 80-100 psig and temperatures of about 140.degree.-170.degree. C. for at least 4 minutes and separating the remaining tea leaf solids from the aqueous solvent to leave a high/temperature pressure aqueous extract. However, the resulting extract was found to have an unacceptable bitter taste with a pruny off-flavour.